This invention is directed to extendible dipper sticks for excavators and backhoes. More specifically, it is directed to a dipperstick with a telescoping member that carries an implement such as an excavating bucket.
Excavators and backhoes are machines used for digging purposes, generally comprised of a tractor carrying a boom that can be pivotally manipulated, the boom in turn carrying a pivotally attached dipperstick. The dipperstick is in effect a secondary boom, carrying an excavating bucket or other implement on one end which is manipulated for digging purposes.
Dippersticks that are extendible are in general comprised of two major components, namely a main housing and a telescoping member. The housing is connected to the boom, and the telescoping member carries the excavating bucket. The bucket is attached pivotally to the end farther from the boom, and is manipulated by a driving means, usually a hydraulic cylinder (bucket cylinder) attached to the telescoping member, the telescoping member itself being extended and retracted by means of another driving means (such as a hydraulic extension cylinder) carried by said main housing.
A common configuration of the telescoping member and main housing is coaxial, with the telescoping member and extension cylinder within the main housing. It is desirable to hold the bucket or other implement in fixed relationship with respect to the telescoping member as the latter is extended and retracted, and since the main housing is in general not large enough to accommodate the bucket cylinder, which controls said relationship, the bucket cylinder must be connected to the telescoping member from without the main housing. For this purpose a slot is often provided, running the length of the main housing, through which the bucket cylinder and telescoping member may be connected. A problem caused by this approach is the structural weakening of the main housing caused by the slot, resulting in premature wear of the housing. If the housing is formed from heavier material to counteract this structural weakness, the construction is made more expensive and the added weight requires greater energy in the manipulation of the main housing while excavating. A further problem caused by this arrangement is that the length of the slot limits the range over which the telescoping member can be extended or retracted. Since the bucket cylinder, as abovementioned, is connected to the telescoping member through the slot, the range of movement of the telescoping member is defined by the points at which the means for such connection abuts either end of the slot. This limits the range over which excavation may be had for a given position of the excavator or backhoe, and places undesirable limitations on the length of the dipperstick's power stroke, lessening its utility, especially when digging in heavy soils.
Another method of attaching the bucket cylinder (on the exterior of the main housing) to the telescoping member (on the interior of and coaxial to the main housing) is to provide a means for carrying the bucket cylinder attached to the telescoping member only at the end that protrudes from the main housing, i.e. adjacent the bucket, and to stabilize said means by slidably attaching it to the main housing at the end thereof closer to the boom. A problem with this configuration is that such a bucket-carrying means adds expense and weight to the telescoping extension, making it less efficient to operate. Moreover, this configuration entails more wear surfaces, requiring greater maintenance.
An attempt to avoid these problems involves a configuration wherein the bucket cylinder is carried by the telescoping member by a means contained within the main housing, such as in the invention disclosed by Beaton in U.S. Pat. No. 3,700,126. The result is that the housing must therefore be made with a larger diameter to accommodate said means, adding weight, cost and inefficiency to the device. Furthermore, the connection between the bucket cylinder and the bucket or implement must be made closer to the pivotal axis of the bucket, requiring higher torque for bucket rotation and therefore more strain on the bucket cylinder.
Another variation of dipperstick utilizes a telescoping member that is coaxial with but exterior to an inner member, which inner member is connected to the boom. This type of device is shown in the invention disclosed by Sampo et al in U.S. Pat. No. 3,445,015. This solves some of the problems of the reverse configuration, but creates the problem of having a larger, heavier telescoping member, requiring greater energy to drive and putting greater strain on the smaller, lighter inner member. Another problem with this variation is that the retraction of the telescoping member is limited by the point at which the inner member is connected to the boom, making the retracted configuration less compact overall and limiting both the digging range of the excavator or backhoe and the length of the power stroke when breaking earth.
In all of these dipperstick devices there is the problem of constant wear on the telescoping member and the main housing (or the inner member in Sampo) due to the sliding friction encountered in operation. In coaxial configurations relatively little volume may be utilized for friction-reducing devices, because greater volume requires greater amount and weight of materials.
It is therefore an object of this invention to provide an extendible dipperstick for excavators and backhoes wherein the main housing and telescoping member are not coaxial.
Another object of this invention is to provide an extendible dipperstick wherein the bucket cylinder is carried by the telescoping member without structural weakening of the main housing.
A further object of this invention is to provide an extendible dipperstick wherein the bucket cylinder is carried by the telescoping member without the necessity of an additional bucket-carrying structure contacting or sliding against the main housing, allowing for lower weight, less materials, and less maintenance.
An additional object of this invention is to provide an extendible dipperstick wherein the main housing and telescoping member are slidably attached in a noncoaxial parallel fashion.
It is another object of this invention is to provide an extendible dipperstick wherein wear due to friction between the telescoping member and main housing is minimized through the use of bearings.
A further object of this invention is to provide an extendible dipperstick wherein the telescoping member is relatively light with respect to the main housing, allowing for less strain on the main housing and greater efficiency in operating the telescoping extension.
An additional object of this invention is to provide an extendible dipperstick wherein the bucket cylinder is carried by the telescoping extension without increasing the torque required to manipulate the bucket or implement, allowing for reduced strain on the bucket cylinder and related structure.
Another object of this invention is to provide an extendible dipperstick wherein the range of movement of the telescoping member is limited neither by the means for mounting the dipperstick to the boom nor by the means for connecting the bucket cylinder to the telescoping member, allowing for greater digging range and a longer power stroke.
A further object of this invention is to provide an extendible dipperstick which may utilize a telescoping extension cylinder for extending and retracting the telescoping member, thereby further increasing said digging range and power stroke.
Other objects, advantages, features and results will more fully appear in the course of the following description.